General Virology Flashcards
Composition of capsid
It is composed of a number of repeating protein subunits called capsomeres.
Functions of capsid
- Protects nucleic acid core from external environment
- Antigenic and specific for each virus
- In non-enveloped tissues initiates first step of viral replication
Icosahedral symmetry
All DNA viruses except poxvirus and most RNA viruses
Helical symmetry
Few RNA viruses - Myxovirus, Rhabdovirus, Filovirus, Bunyavirus
Complex symmetry
Poxvirus
Virus with >1 kind of peplomeres
Influenza virus - hemagglutinin and neuraminidase peplomeres
Non-enveloped DNA viruses
Parvovirus
Adenovirus
Papovavirus
Non-enveloped RNA viruses
Picornavirus Reovirus Calicivirus Hep A Hep E
Bullet shaped virus
Rabies
Filamentous virus
Ebola
Brick shaped virus
Poxvirus
Space vehicle shaped virus
Adenovirus
Wheel shaped virus
Rotavirus
Rod shaped virus
Tobacco mosaic virus
Viroids?
- Have naked, circular, small ssRNA without capsid.
- Seen in plants
- Depend on host enzymes for replication
Prions
- Abnormal infectious protein without nucleic acid
- Resistant to physical and chemical agents
- Cause prions disease
Families in DNA viruses
6 Herpesviridae Hepadnaviridae Parvoviridae Papovaviridae Poxviridae Adenoviridae
Nucleic acid for Herpesviridae
ds, linear
Nucleic acid for Hepadnaviridae
ds, circular, incomplete
Nucleic acid for Parvoviridae
ss, linear
Nucleic acid for Papovaviridae
ds, circular
Nucleic acid for Poxviridae
ds, linear
Nucleic acid for Adenoviridae
ds, linear
Viruses in Herpesviridae family
HSV-1, HSV-2
Varicella Zoster
Epstein-Barr
Cytomegalovirus
Viruses in Papovaviridae family
Human papillomavirus
JC virus
BK virus
Viruses in Poxviridae family
Variola (smallpox)
Molluscum contagiosum virus
Families in RNA viruses
13 Arenaviridae Bunyaviridae Coronaviridae Caliciviridae Flaviviridae Filoviridae Orthomyxoviridae Picornaviridae Paramyxoviridae Rhabdoviridae Reoviridae Retroviridae Togaviridae
RNA families with ss +ve sense RNA
Picornaviridae Caliciviridae Togaviridae Flaviviridae Coronaviridae
RNA families with ss -ve sense RNA
Rhabdoviridae Filoviridae Paramyxoviridae Orthomyxoviridae Bunyaviridae Arenaviridae
RNA family with dsRNA
Reoviridae
Nucleic acid in Retroviridae
2 identical copies of +sense ss linear RNA
Viruses in Picronaviridae family
Polio Coxsackie Echo Entero Rhino Hep A
Viruses in Caliciviridae family
Norwalk
Hep E
Viruses in Togaviridae family
Rubella
Eastern and Western equine encephalitis virus
Viruses in Flaviviridae family
Dengue
Yellow fever
West Nile
Hep C
Viruses in Coronaviridae family
SARS-CoV
MERS-CoV
Viruses in Rhabdoviridae family
Rabies
Vesicular stomatitis virus
Viruses in Filoviridae family
Ebola
Marburg
Viruses in Paramyxoviridae family
Mumps Measles Parainfluenza Nipah Hendra Respiratory Syncytial Virus
Viruses in Orthomyxoviridae family
Influenza A, B, C, D
Viruses in Bunyaviridae family
Hanta
Sandfly fever virus
Viruses in Arenaviridae family
Lassa fever virus
Lymphocytic choriomeningitis virus
Viruses in Reoviridae family
Rotavirus
Reovirus
Colorado tick fever virus
Viruses in Retroviridae family
HIV
HTLV (Human T Lymphotropic Virus)
Examples of attachment
HIV: Viral surface glycoprotein gp120 binds to CD4 of host
Influenza: Viral hemagglutinin binds to glycoprotein receptors on respiratory epithelium
Site of nucleic acid replication
DNA - nucleus except Poxvirus
RNA - cytoplasm except Retrovirus and Orthomyxovirus
Site of assembly
DNA viruses - nucleus except Poxvirus and Hepadnavirus
RNA viruses - cytoplasm
Examples of Defective or Dependoviruses
Hep D requires help of Hep B
Adeno-associated satellite viruses need help of Adenovirus
Define inclusion bodies
Aggregates of virions or viral proteins and other products of viral replication that show altered staining pattern.
They may be inside host cell cytoplasm/nucleus/both.
Intracytoplasmic inclusion bodies
Acidophilic, seen as pink structures when stained with Eosin Methylene blue stain.
Ex: Poxvirus, Rabies
Intranuclear inclusion bodies
Basophilic
Cowdry Type A: vary in size with granular appearance
Cowdry Type B: circumscribed amorphods or hyaline spheres.
Intracytoplasmic inclusion bodies examples
Negri bodies - Rabies
Paschen bodies - Variola
Bollinger bodies - Fowlpox
Molluscum bodies - molluscum contagiosum virus
Cowdry Type A inclusion bodies examples
Torres body - yellow fever virus
Lipschultz body - HSV
Cowdry Type B inclusion bodies examples
Poliovirus
Adenovirus
Intracytoplasmic and Intranuclear inclusion bodies examples
Owl’s eye appearance - cytomegalovirus
Measles virus
Stain used in EM
Potassium Phosphotungstate
Direct virus detection from specimen in EM is used for
Viruses that are difficult to cultivate
Ex: Rotavirus, Hep A, Hep E from faeces
CMV from urine
Applications of fluorescent microscopy
Dx of Rabies virus Ag from skin biopsies/corneal smear
Dx of Adenovirus from conjunctival smear
Detection of Viral Ag examples
- HBsAg and HBeAg Ag detection
- NS1 Ag detection for Dengue virus
- SARS-CoV2 Ag by immunochromatographic assay
- p24 Ag for HIV
Detection of Viral Ab examples
- Anti-HBc, Anti-HBs, Anti-HBe Abs in serum for Hep B
2. Abs against HIV-1, HIV-2
Yolk sac inoculation can be used for
Arbovirus,
Some bacteria like Rickettsia, Chlamydia, Hemophilus ducreyi
Amniotic sac inoculation can be used for
Influenza virus
Allantoic sac inoculation can be used for
Viral vaccines like influenza, yellow fever vaccine
Chorioallantoic membrane inoculation can be used for
Poxvirus
Organ culture used for
Fastidious viruses with affinity to specific organs
Ex: Tracheal ring culture for coronavirus
Explant culture used for
Adenoid explants used for adenovirus
Primary cell lines with examples
Derv. from normal cells
5-10 divisions
Diploid karyosome
Ex: Monkey kidney cell line for Myxovirus, Enterovirus, Adenovirus
Human amnion cell line
Chick embryo cell line
Secondary cell lines with examples
Derv. from normal cells
10-50 divisions
Diploid karyosome
Ex: Human fibroblast cell line for recovery of CMV
MRC-5 and WI-38
Continuous cell lines with examples
Derv. from cancerous cell lines
Immortal
Altered haploid chromosome
Ex: HeLa cell line
HEp-2 cell line
KB cell line
Inactivated vaccines examples
- Rabies neural vaccine (Semple vaccine, BPL vaccine) - derv. from sheep brain
- Rabies non-neural vaccine
a. Purified Chick Embryo Cell (PCEC) vaccine - from chicken fibroblast cell line
b. Human Diploid Cell vaccine - form human fetal lung fibroblast cell line
Subunit vaccine examples
Presents Ag to immune system w/o pathogen particles
- Hep B surface Ag - from yeast
- L1 protein for papillomavirus - from yeast
Live attenuated vaccine examples
Mumps Measles Rubella Chickenpox Smallpox Rotavirus Adenovirus
Live inactivated vaccine examples
- Polio - Live Oral Polio Vaccine, Killed Injectable Polio Vaccine
- Influenza - Killed and live attenuated (intranasal)
- Hep A - Inactivated, live attenuated